After installing ffmpeg from svn with checkinstall, I had the problem that the also installed library libavcodec51 is not compatible with the one delivered with Ubuntu. But I could not simply uninstall it so that the manually installed version was used because that caused problems with libxine1-ffmpeg, which stopped kaffeine, amarok and other software from running properly.

Unfortunately, checkinstall's --provides option did not work as expected. So I had to find a way to have them use the manually installed version I compiled from svn and hiding that fact that my package manager. I had to let the package management system know the package was already installed.

So I ended up creating an artificial package that only has the same name and a similar package version, but no actual contents. Create an empty directory, place the following Makefile into it and execute the following checkinstall command. You may need to adjust the parameters for different packages, refer to the output of apt-cache policy somepackage for an appropriate version number)